NAIROBI: The United States on Wednesday warned that bad governance was holding back Africa, with Secretary of State Hillary Clinton personally pressing leaders in regional power Kenya to better share power.

Clinton launched a wide-ranging Africa tour at a regional conference in Kenya, whose favourite son -- US President Barack Obama -- underscored the message in a surprise video.

"Only Africans can unlock Africa's potential," Obama said, returning to the theme of good governance he made on his first presidential visit to the continent last month in Ghana.

"To all Africans who are pursuing a future of hope and opportunity, know this: you have a partner and a friend in the United States," said Obama, whose father was born in Kenya.

Clinton, addressing the forum of some 40 nations that enjoy preferential access to the US market, said the United States sought to be a "partner, not patron" of the continent.

"True economic progress in Africa will depend on responsible governments that reject corruption, enforce the rule of law, and deliver results for their people," Clinton said.

"This is not just about good governance -- it's also about good business," said Clinton, who arrived here Tuesday.

The 11-day trip, which comes just three weeks after Obama visited the continent, is Clinton's longest since she became the top US diplomat six months ago and her first to sub-Saharan Africa.

Clinton held a rare joint meeting with Kenyan President Mwai Kibaki and Prime Minister Raila Odinga, pressing them to implement key points of a power-sharing deal that ended a cycle of deadly electoral violence last year.

She cited her own experience emerging from arch-rival during the US presidential primary to close ally of Obama, saying that onetime foes can work together for a nation's good.

Kenya is a longtime US ally but Washington has been concerned about impunity for those who foster violence as well as corruption -- issues that analysts believe kept Obama from picking Nairobi for his emblematic first Africa trip.

A US official who attended the meeting said that Clinton was "very direct" and that the two Kenyan leaders, former political foes, "surprisingly" were not defensive.

Odinga had a day earlier criticised the US stance, saying that Kenya would not be told what to do.

Another senior US official said on condition of anonymity that Odinga's remarks were "public posturing" and voiced confidence that the two leaders would implement reforms in due time.

"I think our encouragement and pressure is important in the broader context -- it tells the leadership, do what your people want you to do," he said.

Kibaki and Odinga, in separate speeches to the gathering, acknowledged the problems in African economies but appealed to the United States to step up investment.

"There are constraints on both the supply and demand side which need to be addressed urgently to enable African countries to take full advantage of the huge American market," Kibaki said.

Clinton later signed an agreement to start negotiations on an investment treaty with Mauritius, hailing the island state as a model of democracy and good governance.

A pressure group promoting Africa's development and supported by U2 frontman Bono, applauded the US emphasis on rooting out corruption, saying it was a prerequisite for reducing poverty.

Clinton later toured an agricultural research institute in Nairobi, where she met with researchers developing high-yield and drought-resistant crops.

Standing amid tall stocks of maize next to the US and Kenyan agriculture ministers, Clinton vowed a new US approach to help the nearly billion people in the world who suffer chronic hunger.

Thirty nations agreed last month to a plan championed by Obama to pump 20 billion dollars into poor nations' agricultural capacities -- rather than relying on emergency food handouts.

Clinton said the plan was a "signature" priority for the administration.

"We are convinced that investing in agriculture is one of the most high-impact, cost-effective strategies available for reducing poverty and saving and improving lives," Clinton said.